When i connect to my Ultravnc server, it works perfect during 10-15 seconds and after that, i do not receive any update on the screen. I still can control the computer where the server is located, but i do not see what i am doing.

Because this is happening on two different computers i am not sure if the problem is on both servers, on my firewall or maybe on the client (but i have tried with 3 and same thing happened).

The installer have the options upgrade -> files are replaced on boot when in use.You can run the installer from vnc, new version become active after reboot.BUT... still RC... if you don't have access at all wait.